Nine farms in Northern Ireland used the same contaminated animal feed which led to a recall of all pig products processed in the Republic, it emerged today.

The North's Agriculture Minister Michelle Gildernew confirmed restrictions have been placed on the farms which were identified by her department's electronic monitoring system.

The move follows the withdrawal of all pork products sold and exported from the Republic after a toxic substance was identified in a feed which was supplied to 10 pig farms in the south of the country.

The Food Safety Authority Ireland (Fsai) insisted health risks to the public were minimal and claimed the withdrawal was a precautionary measure.

Ms Gildernew said restrictions were put in place on Friday night when the situation began to unfold.

"To date nine farms in the north have been identified as having used the contaminated feed," she said.

"We are supplying the Fsa with all the necessary information to allow them to take an informed decision."

Ms Gildernew said she has been in contact with her counterpart in the Republic, Agriculture Minister Brendan Smith, who updated her on the rationale for the decision taken by the Dublin authorities to recall all stocks bought since September 1.

"My officials have been in close contact with their counterparts in the Department of Agriculture, Fisheries and Food (DAFF) since this situation developed," she continued.

"There is obviously a large amount of north south movement of these products in Ireland and we need to carefully consider the way ahead."

Ms Gildernew said she has also kept the North's Health Minister Michael McGimpsey up to date with developments.

"I want to ensure the Health Minister is fully briefed so that decisions can be taken and consumers can be kept informed," she added.

Pork and bacon products from the Republic were pulled from supermarket shelves across Europe when it was confirmed dioxins in some products were between 80 and 200 times over acceptable levels.

Further investigations revealed breadcrumbs used in an animal feed distributed by one licensed supplier tested positive for non-dioxin-like polychlorinated biphenyls (PCBs) - which are banned.

The feed producer - who made the breadcrumbs from recycled bread and dough - was closed down in the middle of last week and restrictions placed on all farms he supplied in southern Ireland.

The Fsai said it appears that some kind of industrial oil tainted the ingredient.

Spokesman Alan Reilly said it was unclear how the contamination got in to the animal feed.

"That's under investigation at the moment," he said.

However, health experts said that despite the high levels of toxic substances found in pork products, consumers will suffer no harmful effects.

The Republic's chief medical officer Dr Tony Holohan said although some types of dioxins can cause cancer, that would only happen after prolonged exposure to higher levels.

"The levels of exposure are not of a level that will be a concern to their health," he said.

"It would be exposure over years for levels to build up to cause the kind of health effects that could occur, like cancer."

Chris Elliott, Professor of Food Safety at Queen's University Belfast, said while consumers want, and deserve, food free from chemical contaminants, in this case there does not appear to be any significant risk to health from consumption of the tainted pork products.

"The contamination of the animal feed itself appears to be the cause of this food scare, as is often the case; it also appears to be limited to the product of one supplier and it should therefore be a quick and simple task to track down the cause of the problem," he added.

The Fsa said it was advising UK consumers not to eat any pork products that originated from Northern Ireland or the Republic of Ireland.

It said it was making the precautionary recommendation while it continued to investigate whether any contaminated pork products had entered the UK market.

A statement said: "The Food Standards Agency is today advising consumers not to eat pork or pork products, such as sausages, bacon, salami and ham, which are labelled as being from the Irish Republic or Northern Ireland, while it continues to investigate whether any products contaminated with dioxins have been distributed in the UK.

"From the information that we have at this time, we do not believe there is significant risk to UK consumers as adverse health effects from eating the affected products are only likely if people are exposed to relatively high levels of this contaminant for long periods.

"This precautionary advice had been issued following the Irish Government's announcement that it is recalling all pork products made in the Irish Republic since September after dioxins were found in slaughtered pigs that are thought to have eaten contaminated feed.

"Dioxins are chemicals that get into food from the environment and they are associated with a range of health effects when there is long term exposure to them at relatively high levels.

"The Agency is continuing to monitor the situation and is in close contact with the Food Safety Authority of Ireland. If it is confirmed that any affected products have been distributed to the UK the Agency will take appropriate action to protect consumers. An urgent meeting of the UK food industry is being organised by the Agency as part of its investigation into possible distribution channels in this country."